1. Field of the Invention:
The present invention relates to a device for calibrating a chassis dynamometer.
2. Description of the Prior Art:
As the regulations regarding the exhaust gas of automobiles has become stricter in recent years, higher precision in measuring of the exhaust gas contents has become more important and, since the operating condition of an automobile during exhaust gas measurement is determined by a chassis dynamometer, the precision of the chassis dynamometer is very important and it must be periodically calibrated. The calibration of a chassis dynamometer comprises calibrating its speedometer and brake horse power.
Conventionally, calibration of a chassis dynamometer has been made by employing analogue measuring devices such as tachogenerator, millivolt meter, etc, requiring a lot of processes and a large amount of man power. Nevertheless, the precision of calibration by the conventional method is not good and, if good calibration is to be made, the measuring devices themselves must be cared for with periodical precision maintenance. In the conventional calibration of a chassis dynamometer, rollers of the chassis dynamometer are first driven by a real automobile or a driving means equipped with a drive wheel or wheels which are particularly adapted to drive the rollers of the chassis dynamometer for the purpose of calibration. The rollers are driven up to a rotating condition which corresponds to a vehicle speed of 100 Km/h and then the automobile or the special driving means is swiftly lifted up by a jack driven by man power so that the driving wheels are swiftly disengaged from the rollers of the chassis dynamometer. This operation is very dangerous. To solve this problem in the aforementioned method and to improve the precision of calibration, an improved device for calibrating a chassis dynamometer has been proposed in Japanese Patent Application 88934/72, which comprises a driving source which rotates rollers of a chassis dynamometer, a pick up means which detects pulses generated in proportion to the rotation of said rollers, a digital computer including a digital counter and a trigger signal adjustor for computing speed and power absorption, a jack for disengaging said driving source from said rollers and associated compressor and oil hydraulic or air pressure means, and a control panel for controlling the aforementioned mechanisms and measuring devices.
In this prior device for calibrating a chassis dynamometer, after the rollers of the chassis dynamometer have been driven by the driving wheels of the driving source up to a predetermined high rotation, the axle of the driving wheels is lifted up by said oil or air pressure means to disengage the driving wheels from the rollers. In this case, in order to remove the driving wheels from contact with the rollers, the aforementioned oil or air pressure means must support not only the weight of the driving wheels and the axle but also the weight of the frame of the driving source (body or frame of an automobile or a special driving structure). Therefore, the oil or air pressure means must be of a large capacity if the jack-up operation is to be swiftly accomplished.
Therefore, it is the object of the present invention to solve the aforementioned problems and drawbacks in the conventional and formerly proposed devices for calibrating a chassis dynamometer and to provide an improved device therefor.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
According to the present invention, the abovementioned object is accomplished by a device for calibrating a chassis dynamometer, comprising: a drive source including a drive wheel adapted to be pressed against rollers of said chassis dynamometer by its own weight and spring force so as to drive and rotate said rollers, and a frame which carries said drive wheel via a spring which exerts said spring force; a fluid pressure operated jack which selectively lifts up said drive wheel so as to terminate the driving contact between said drive wheel and said rollers; a stay which bears a part of force which would be exerted to said drive wheel due to the weight of said frame; a pick-up means which detects pulses generated in proportion to the rotation of said rollers; a digital computer including a digital counter and a trigger signal adjustor for processing the pulses detected by said pick up means to compute the driven speed of and power absorption by the chassis dynamometer; and a control panel for controlling said jack and said computer.
When calibration is made by employing the device of the aforementioned combination, after the rollers of the chassis dynamometer have been driven by said driving wheel up to a predetermined rotation, the jack is operated to lift up the drive wheel to disengage it from the rollers. In this case, since the weight of the driving source frame is partially supported by the stay, when the jack carries the weight of the driving wheel and its axle and lifts them up against the spring force of the spring, the driving wheel can be disengaged from the rollers before the jack completely suspends the frame of the driving source frame. Thus, it is possible to perform the jacking-up operation swiftly by employing a jack of a relatively small capacity. Furthermore, the stay provides for an additional stabilizing support of the driving source and improves safety in calibrating the operation of the chassis dynamometer.
According to a particular feature of the present invention, the stay may preferably be adapted to engage said frame at a location adjacent said drive wheel and carry said portion of the vehicle at a fixed vertical position with respect to said rollers, said position being intermediate the two extreme positions where the drive wheel suspended by said spring just contacts with said rollers and where the frame is completely suspended by the driving wheel via said spring.
According to another feature of the present invention, said drive source may conveniently be an automobile including a body which serves as said frame, a pair of drive wheels adapted to be driven by an engine mounted on said body, said drive wheels serving as said drive wheel which drives and rotates said rollers, and a pair of suspension springs which suspend said body against an axle for said pair of drive wheels. In this case, said fluid pressure operated jack may preferably be adapted to lift up said axle by means of an arm which is pivotably mounted to said body at one end thereof and supported by said jack at the other end thereof.